Solid state drives (SSDs) based on flash memory technology can be more expensive than hard disk drives (HDDs) in terms of cost per unit bit storage. To reduce the cost of SSDs, it is desirable to develop low-cost memory fabrication processes as well as new memory architectures for improving the storage density.
One such effort is to create multi-bit data storage memory devices to achieve a higher storage density. The fabrication of multi-bit (or multi-level cell (MLC)) flash memories can require precise deposition of multiple semiconductor layers and multiple overlay lithography processes to create complicated memory transistors consisting of multiple floating gates and blocking and tunneling layers. This significantly increases the complexity of the memory cells. While MLC flash memories are developed to enable low-cost manufacturing of such complicated cells, the future scale-down of MLC circuits may require new MLC with simpler architectures as well as updated manufacturing systems with lower processing cost and higher throughput.
Recent efforts have demonstrated other multi-bit memories based on different materials and device structures, including memories based on organic semiconductors with ambipolar transport properties, memory transistors based on nanostructured materials, flash memory-like transistors with capacitively coupled nanoparticle (NP)-based floating gates, and multi-level resistive memories based on phase-change materials. However, relatively complicated and expensive processes are still required to make these devices.
This section provides background information related to the present disclosure which is not necessarily prior art.